The present invention relates to the field of mobile telephony networks and more particularly to a device, a system and an associated method for ensuring continuity of telephony services on the network.
Mobile telephony networks comprise an important item of equipment, called the nominal location register (HLR—Home Location Register), which officiates as a central database containing all the data relating to each of the subscribers authorised to use the mobile network. This database is generally distributed over several items of HLR equipment for practical reasons of processing and storage capacity. The database is automatically filled when a new subscriber is registered with a telephony operator. The commercial information system (CIS) from which the commercial service proceeds with the contractual registration of the new subscriber updates the HLR database with the new data entered, in particular the allocation of identifiers of this subscriber (IMSI [International Mobile Subscriber Identity] number and MSISDN number corresponding to the call number of the subscriber [Mobile Station Integrated Services Digital Network]). This filling of the HLR database is always at the initiative of the CIS information system.
The HLR register thus formed than has autonomous behaviour. The role of the HLR is to check the location of a subscriber customer and to transmit the data relating to the services and to the rights of the subscriber to other equipment in the network when the location is authorised. One of these other items of equipment referred to is in particular the visitor location register VLR.
When a subscriber is located on a network, he comes under the responsibility of a switch of the MSC (Mobile Switching Centre) mobile service coupled to a VLR register. This MSC/VLR first of all constructs an authentication message in order to verify the identity of the SIM [Subscriber Identity Module] card loaded in the terminal of the subscriber. Once the customer is authenticated the MSC/VLR constructs a location request message that it sends, over a type-SS7 (Signalling System Number 7) signalling network, to the HLR central register of the network of the operator. The HLR register then updates, in the database, the current location of the subscriber.
At the time of location, and therefore after authentication, the HLR register verifies that the subscriber terminal has the right to be located (in particular when it is a case of roaming location) and, where appropriate, transmits the data relating to the services available for the subscriber to the VLR register. Even if the HLR register appears to be a simple database, it is a system that directly receives and processes messages or transactions on the signalling network of the operator. In particular, if the HLR register suffers a fault, the telephony network becomes inactive since only the HLR register manages the location updates of the mobile terminals in a general fashion in the network. When one HLR register out of the plurality of HLRs structuring the network becomes faulty, the result is that some subscribers—those managed by the HLR out of commission—can no longer be located, can no longer be called, send or receive SMS (Short Message Service) messages, or benefit from other services on the mobile telephony network.
To meet this problem, there exist procedures for backup of an HLR register by means of which the configuration data of the faulty HLR, previously saved, are reloaded into a backup HLR register. Nevertheless, this procedure requires a period of a few hours and therefore total unavailability of the network, for the subscribers concerned, during this period of time. There is therefore a need to ensure a minimum service to the subscribers within a short period.
Data backup systems for one or more active HLR registers on another dedicated HLR register officiating as a redundant backup HLR are also known. Since the basic data of HLRs are constantly changing, in particular because of the roaming of the subscribers and therefore the updating of the current location in the database, a dynamic saving of the data to the backup HLR is carried out by synchronisation between the latter and the various active HLRs. When an HLR fails, an appropriate signal is sent and makes it possible to switch from the faulty HLR to the associated backup HLR register. Patent application US-2005/081095 describes a solution comprising such mechanisms.
One disadvantage of this solution concerns the large quantity of resources used, in particular by either the deployment of backup HLRs in large numbers in order to provide redundancy for each of the active HLR registers, or the necessity for a backup HLR provided with high processing capacities so as to manage the synchronisation with all the active HLRs and store all the data thereof. The first aim of the invention is to provide a continuity of service solution requiring limited resources in terms of backup equipment for any one of the HLRs that breaks down.
Another disadvantage of this solution concerns the undesired propagation of malfunctionings or errors. This is because, if a data item happens to corrupt an active HLR register, by dynamic synchronisation of the backup HLR or HLRs, this data item will also corrupt these other backup HLRs, giving rise to total unavailability of the network in the case of failure. Another aim of the invention is thus to offer a more secure solution, in particular against the propagation of erroneous or corrupted data.
Another disadvantage of the solution of the prior art lies in the use of part of the bandwidth for synchronisation between HLRs and for the transmission of updating data between them. This gives rise to a reduction in quality of service during consumption peaks by the subscribers. This also generates unnecessary data traffic since a large number of data on the backup HLR are subsequently modified before the backup HLR is used. Another aim of the invention is therefore to provide a continuity of service solution without impact on the data traffic in normal operation of the network.
At least one of these aims is achieved by the present invention by using, as temporary backup, HLR equipment, possibly initially empty of any user data, which, during non-referenced subscriber location demands, on its own initiative actuates the SIC information system in order to recover a minimum of data allowing the identification of the subscriber on the network and therefore its activation. No synchronisation with the active HLRs is necessary, since the data are recovered when necessary on the information system. In addition, the updating data traffic between active HLRs and backup HLRs is avoided. Such a solution can be implemented rapidly since only a simple configuration is required, limited to ensuring the routing of the messages dedicated to the faulty HLR to the backup HLR taking over.
The invention makes it possible in particular to re-establish a minimum service for the subscribers while awaiting recovering a backup HLR with a more complete configuration. To this end, an object of the invention is first of all a nominal location registration device (HLR-S) on a mobile telephony network, the device comprising user data including their current location in the network and processing means arranged to receive a location demand from a user mobile terminal and update the current location of the mobile terminal, the demand emanating from equipment (MSC/VLR) in the network for location of the subscriber terminal. According to the invention, the processing means are arranged to send, when the device does not comprise data associated with the mobile terminal, a request demanding data on the user to an information system (CIS) comprising data on all the users of the network.
Thus, when the HLR device, for example used as a backup HLR for ensuring continuity of services on the mobile telephony network, receives a location demand concerning a subscriber for whom it does not yet have user data, it proceeds with the recovery of key data (IMSI number, MSISDN, for example) on the information system in order to manage a simplified profile of the user. Thus the latter all the same accesses the network and the basic services defined by this simplified profile.
The invention is distinguished in particular from the known solutions by the actuation of a CIS information system at the initiative of an HLR, the backup HLR in this case, in order to recover user data. This is because the prior art puts forward only an initial supply to the HLRs at the initiative of the CIS, without any subsequent connection occurring. In one embodiment, the processing means are arranged to acknowledge the request to the equipment so as to allow the effective activation of the terminal in the network.
Another object of the invention is a service continuity system on a mobile telephony network comprising at least one normal nominal location register (HLR) and a backup nominal location register (HLR-S), the registers comprising user data and being able to process demands for location of user mobile terminals, the demands emanating from at least one item of equipment (MSC/VLR) on the network, an information system (CIS) comprising data on all the users of the network, and switch means arranged to route, when the normal register (HLR) is faulty, the location demands to the backup register (HLR-S). The invention is particularized in that the backup nominal location register (HLR-S) is arranged to send, on reception of a demand to locate a mobile terminal and when the backup register (HLR-S) does not comprise user data associated with the mobile terminal, a request to demand user data of the information system (CIS).
The backup register HLR thus does not need to be pre-configured. The data relating to the subscribers are enhanced along with new terminal connection and location demands, by the recovery of data from the general information system CIS. When the normal HLR is faulty, the location demands are then re-routed to the backup HLR, an ad hoc configuration being able to be required. The backup HLR then appears in the network as being the active HLR. The location demands, the demands relating to the incoming calls or SMSs are then sent to it. The traditional functioning of the network is consequently only a little altered.
In one embodiment, the user data stored on the registers (HLR, HLR-S) comprise data relating to the current location of the mobile terminals, the registers (HLR, HLR-S) also being arranged so as to update the data relating to the current location during the processing of the location demands. In one configuration of the invention, the normal register is identified on a signalling network (SS7), belonging to the mobile telephony network, by at least one address (generally by an SCCP address and an MPT address for the SS7 network), the location demands being sent over the signalling network to the address, the switching means comprising a user interface arranged to parameterise the backup register with the address so as to route the location demands to the backup register (HLR-S). This configuration of the backup register is advantageously simple to allow the functioning of the solution according to the invention. Because of the parameterising of the backup HLR with the “active”address of the HLR, the location demands are automatically routed to the new active HLR, that is to say the backup HLR brought into service.
A variant of this configuration, applied solely when the failure of the main HLR occurs, consists of pre-parameterising the global routing network in order to take account of a main routing address corresponding to the normal HLR and a second-choice address corresponding to the backup HLR. This default configuration in the network makes it possible, in the event of failure, in order to join an HLR to its MTP address (low-layer SS7 routing), to route as a second choice to the backup HLR (the case of failure of the normal HLR). The network thus automatically proceeds with the routing of the requests or demands to the backup HLR, and no configuration of the backup HLR is then necessary. To this end, the switch means comprise the pre-parameterising of the network by indicating, in the MTP signalling protocol layer of the network, a first address of the normal register and a second address of the backup register, the routing of the location demands on the network automatically switching to the second address when the normal register is faulty.
According to two embodiments:                the backup register (HLR-S) comprises a default profile of services available on the network and is arranged to allocate the default profile to the mobile terminal;        the backup register (HLR-S) comprises a plurality of profiles of services available on the network and is arranged to allocate one of the profiles to the mobile terminal according to data returned by the information system (CIS) in response to the request.        
In the first variant, the management is simplified by the use of a single profile for all the subscribers. This profile allows access to the basic services of the mobile telephony network, in this case the connection and establishment of communication from and to the subscriber. The transmission of SMS messages may possible integrate this profile. In the second variant, several profiles exist, in particular profiles relating to the nature of the subscriptions of the users with a view to invoicing. The HLR register then recovers, on the information system, data from which a profile choice can be made, for example the type of subscription, “prepaid” or “postpaid”, associated with the subscriber.
Another object of the invention is a service continuity method on a mobile telephony network, in which location demands for mobile terminals emanate from at least one item of network equipment (MSC/VLR) in order to be processed by at least one normal nominal location register (HLR), the method comprising a step of routing the location demands to a backup nominal register (HLR-S) when the normal register (HLR) is faulty and, in addition, on reception of a location demand for a mobile terminal, a subsequent step according to which the backup register (HLR-S) sends, when the backup register (HLR-S) does not comprise user data associated with the mobile terminal, a request to demand user data of an information system (CIS) comprising data on all the users of the network.
By this mechanism, the non-preconfigured backup HLR accesses the useful data to effectively permit the maintenance of the minimum services with regard to mobile telephony. The actuation of the information system makes it possible to dispense with extensive hardware resources and synchronised backup operations during the normal functioning of the network. It should be noted that the authentication messages represent approximately 30% to 40% of the number of messages exchanged over an SS7 network,
In one embodiment, the method comprises, prior to the routing step, a step of deactivation of authentication mechanisms of the mobile terminals at the at least one item of network equipment (MSC/VLR). This deactivation limits the exchanges between the VLR equipment and the backup HLR recorder, and consequently also limits the quantity of data to be recovered from the information system CIS (the data relating to identification, for example a secret key, are no longer useful). This limitation of the quantity of data to be recovered proves to be important when setting up the backup register. This is because, on switching to the backup HLR according to the invention, a large number of subscribers then attempt to locate, which gives rise to a large number of connections between this backup HLR and the information system. The deactivated authentication thus makes it possible to avoid overloading the network when the HLR breaks down.
Nevertheless, it is possible to effect the backup without deactivating the authentication. For this purpose the CIS must, in addition to the IMSI, transmit the enciphering key to the backup HLR. The function AuC (Authentication Centre) must, for its part, be activated in the backup HLR so that it can form the authentication triplets and transmit them to the MSV/VLR in order to authenticate the mobile terminal. To permit the rerouting of the location demands to the new backup HLR, it is useful to configure the latter. For this purpose, provision is made for the normal register (HLR) to be identified on a signalling network (SS7), belonging to the mobile telephony network, by an address, the location demands being sent over the signalling network to the address, the method comprising a step of configuring the backup register (HLR-S) with the address in the signalling network so as to route the location demands to the backup register (HLR-S). According to a variant, it is envisaged that the network is pre-parameterised in order to give a main routing address identifying the normal register and a second routing address indicating the backup register, the routing of the location demands on the network being effected, in normal operation, to the main address and automatically switching, when the normal register is faulty, to a routing to the second address.
In one embodiment, the request concerns a demand for a network identifier of the mobile terminal (MSISDN). In a conventional use of the HLR registers aimed at storing the actual location of the subscribers, provision is made for the registers (HLR, HLR-S) to comprise data relating to the current location of the mobile terminals, the method comprising a step of processing the location demand for a mobile terminal by the register receiving the demand, the processing comprising the updating of the current location of the mobile terminal.
In one embodiment, the method also comprises a step of allocating, by the backup register (HLR-S), a profile to the mobile terminal, the profile being a profile of services available on the network. This profile can be defined by default. More particularly, according to an alternative to the single default profile, the profile allocated is chosen from a plurality of profiles according to data returned by the information system (CIS) in response to the request.